I can't find the Retopo menu
The video you mention is very old, it uses blender 2.49 which was before the major interface overhaul that started with blender 2.50. The mesh panel you are looking for had several things grouped together that are now in different places.

The retopology part that you are after is now better defined under snapping options. With transform snapping enabled set the snap element to face and you can have vertices you move snap to an existing surface.

Blendercookie has a more recent retopology video that you should find helpful.